Line 2 baking tins with baking paper and pre-heat the over to 160℃

Cram the softened butter and sugar and mix until combined.

Slowly add the eggs 1 by 1 and mix until smooth.

In a seperate bowl, mix the boiling water and instant coffee. Add this to the cake mixture and mix thoroughly for several minutes.

Sift the flour, baking powder and Xanthan Gum into the mixture. Use a metal spoon to fold the mixture in.

Spoon the mixture evenly between the two cake tins before placing them into the oven for around 25 minutes. Check the mixture is cooked with a cake tester. If any mixture comes out on the tester, place the cake back into the over for 2-3 minutes and repeat.

When the cakes are cooked, remove them from the baking tins and place on a wire rack to cool.

Create the icing by creaming butter until it turns pale. Slowly add in the icing sugar and continue to mix.

In a seperate bowl, mix the boiling water and instant coffee then add this slowly to the icing mix.

When the cakes have cooled, spread a layer of icing on top of one of the cakes, and stack the other on top. Continue to add icing to the top of the cake and decorate with walnuts before serving.

If you wish to ice the whole cake, including the sides, double the icing recipe.